Bar press with hydraulic drive

ABSTRACT

The invention relates to a bar and tube extruding press for forming metal ingots into profiles, tubes, bars or the like, comprising a male die and a female die, through which a metal ingot can be pressed by means of the male die, comprising a container, and comprising a driving device, in which the driving device comprises at least one main cylinder for applying the main pressing force of the male die to the metal ingots, characterized in that on the one hand the driving device comprises at least one speed-controlled internal gear pump for providing the hydraulic oil to the at least one main cylinder, by means of which the at least one main cylinder can be driven, and in that on the other hand the driving device additionally comprises at least one hydraulic advance and/or return cylinder for moving the male die in relation to the female die or at least one electrical drive for moving the male die in relation to the female die, by means of which the male die can he moved into a position in which the speed-controlled internal gear pump only then interacts with the at least one main cylinder in such a way that the main pressing force is applied to the male die by means of the at least one main cylinder.

FIELD OF THE INVENTION

The invention relates to a bar and tube extruding press for formingmetal ingots into profiles, tubes, billets, or the like, comprising amale die and a female die, through which a metal ingot can be pressed bymeans of the male die, comprising a ingot container, and comprising adriving device, in which the driving device comprises at least one maincylinder for applying the main pressing force of the male die to themetal ingots.

PRIOR ART

Such bar and tube extruding presses have been known for decades in priorart and are used for producing the most varied components from typicallymetallic materials, which are pressed through a female die and subjectedto forming at a high degree of deformation.

Main features of conventional bar extruding presses are an ingot loaderbetween the male die and the ingot container and the generation ofpressing force using a main cylinder and an advance and/or returncylinder, wherein all auxiliary movements, including the adjustment ofthe bar extruding press to various ingot formats and feeding the metalingots to the female die, are performed by hydraulic cylinders. The sizeof the hydraulic drive is determined by the pressing force to be appliedby the bar and tube extruding press and optionally by the pressing speedrequired for the desired forming process.

In the past decades, the known bar and tube extruding presses werefurther developed into so-called short stroke extruding presses in whichingot length increased and the main cylinder stroke was designed for aspecific ingot length, particularly by providing a compact press frame.The ingot loader was disposed between the female die and male die in aso-called front loader design, and symmetrical ingot upsetting wasperformed. The hydraulic drives and reservoirs required for moving theindividual components of the bar and tube extruding press and forapplying the pressing force were disposed at the periphery of the movingcomponents.

Such bar extruding presses typically apply pressing forces of about 10to more than 160 MN. Large bar extruding presses with pressing forces of100 MN can form ingot lengths of more than 2,000 mm at an ingot diameterof more than 1,000 mm. Such extruding presses are known, for example,from patent specifications DE 10 227 488 B3 or EP 1 526 930 B1.

In prior art, the hydraulic oil is delivered to the hydraulic driveand/or the means for applying the pressing force between the female dieand the male die using axial piston pumps. But such axial piston pumpsare relatively expensive. Furthermore, they have the disadvantage thatthey are characterized by high pulsation rates, particularly at lowspeeds, which eventually does not only result in undesirable vibrationsbut in a relatively high noise level. For industrial safety reasons,such bar and tube extruding presses typically comprise fairlysophisticated noise protection measures. In addition, the known bar andtube extruding presses have a relatively high power consumption.

PROBLEM OF THE INVENTION

It was therefore the problem of the invention to provide a bar and tubeextruding press for forming metal ingots that can overcome thedisadvantages known from prior art.

This problem is solved according to the invention by a bar and tubeextruding press including the features of claim 1. Advantageousembodiments of the invention are described in the dependent claims.

SUMMARY OF THE INVENTION

According to the invention, the driving device comprises on the one handat least one speed-controlled internal gear pump for providing thehydraulic oil to the at least one main cylinder, by means of which theat least one main cylinder can be driven, and on the other hand thedriving device additionally comprises at least one hydraulic advanceand/or return cylinder for moving the male die in relation to the femaledie or at least one electrical drive for moving the male die in relationto the female die, by means of which the male die can be moved into aposition in which the speed-controlled internal gear pump only theninteracts with the at least one main cylinder in such a way that themain pressing force is applied to the male die by means of the at leastone main cylinder.

Such a design of the driving device of the bar and tube extruding pressmakes it possible to use standard electrical motors with higher massmoments of inertia in combination with smaller dimensioned frequencyconverters for operating the speed-controlled internal gear pump(s).

This has the advantage that the driving device can be provided at aneven lower cost to the bar and tube extruding press.

According to the invention, the expression “smaller dimensionedfrequency converters” means such frequency converters which normallywould not be properly dimensioned for the selected size of standardelectrical motors.

This particular interaction of a standard electrical motor that isoversized with respect to a frequency converter and such a frequencyconverter, or vice versa, becomes possible because the speed-controlledinternal gear pump is substantially exclusively used for applying themain pressing force, wherein the main pressing force is only transmittedto the male die by means of the at least one main cylinder after themale die has been moved into a specific position. This movement of themale die into this specific position is performed using the at least onehydraulic advance and/or return cylinder or the at least one electricdrive.

The at least one hydraulic advance and/or return cylinder or the atleast one electric drive are a simple design for bringing about veryfast movements of the male die in the auxiliary process time relative tothe transmission of the main pressing force.

This design is in contrast to the previously common procedures in whichspecial servo drives with a low mass inertia are used.

In general, simple and already commercially available devices are usedhere to effect smaller losses when switching off the pumps than could beachieved using a drive without variable speed and axial piston pumps.This allows extremely energy-efficient operation of the bar and tubeextruding press.

In addition, frequent switching on and off is no problem, and volumeflow can easily be adjusted by changing the speed.

Finally, such internal gear pumps are much more silent than axial pistonpumps, which is why the typical noise protection equipment used with barand tube extruding presses can be eliminated or implemented in a muchmore simple and space-saving manner.

The use of speed-controlled internal gear pumps also allows a simple androbust design of all components and provides a drive system that is easyto service and comprehend.

Such internal gear pumps, which are known in many designs from priorart, are particularly suitable for use with variable-speed drives andhave proven their special fitness with respect to load cycles and powerconsumption.

It is further very advantageous that the present bar and tube extrudingpress can also do without additional hydraulic control blocks or thelike, which otherwise are imperative for switching the at least oneinternal gear pump between the at least one main cylinder and at leastone side cylinder or container moving cylinder or the like.

In this respect, this is particularly an improvement of hydraulicefficiency.

According to the invention, minimization of purchasing costs, low noiseoperation of the systems, good efficiency in combination withenergy-efficient operation, and minimization of pulsation at low speedscan be achieved.

The device according to the invention particularly allows a completestandstill of the pump drives when no pressurized hydraulic oil has tobe supplied.

This results in a power saving potential of about 33% to 55% compared toconventional bar presses.

We would like to point out here once again that the at least onespeed-controlled internal gear pump is preferably just used for theforming process proper and, if required, for an extrusion butt shearingprocess.

It is preferred that the at least one frequency-controlled internal gearpump can be controlled, using a suitably designed controller of the barand tube extruding press, such that the combination of the number ofinternal gear pumps used and frequency selected ensures the bestpossible efficiency.

For this purpose, the associated characteristics of the internal gearpumps were previously calibrated using a suitable test rig device or thelike, as a function of pressure and rotational speed.

The resulting array of characteristic curves is stored in a suitablemanner in the controller of the bar and tube extruding press.

It is therefore particularly advantageous that a theoretical value ofthe delivery quantity and the number of internal gear pumps is firstcalculated in real time by linear interpolation in a two-dimensionalfield. This can later be fine-tuned using a control device designed forthis purpose.

This pilot control provides very accurate and fast speed control in theactual pressing process.

It should be noted here once again that it is particularly advantageousthat at least one hydraulic advance and/or return cylinder is providedto move the male die relative to the female die.

The result is particularly that the main pressing force is transmittedusing one or several main cylinders, but the male die is advanced andreturned relative to the female die into and out of a position in whichtransmission of the pressing force is to start using preferably smalleradvance and return cylinders.

In other words, the driving device includes at least onespeed-controlled internal gear pump for supplying hydraulic oil to theat least one main cylinder with which the main pressing force istransmitted, and at least one hydraulic advance and/or return cylinderfor moving the male die relative to the female die or at least oneelectric drive for moving the male die relative to the female die, tomove the male die into a position at which the transmission of the mainpressing force starts.

In this way, the quantity of hydraulic oil to be delivered over theentire operation of the bar and tube extruding press is limited to theminimum required for such driving concepts.

Furthermore, the internal gear pump only has to be driven at a higherdrive performance when main pressing forces actually have to be appliedat the bar and tube extruding press, that is, when a main pressing forcemust be transmitted to the male die using the at least one maincylinder. Otherwise the internal gear pump can be driven at asignificantly reduced drive performance. Or the internal gear pump iscompletely out of service. This makes the operation of the drivingdevice or the entire bar and tube extruding press much more efficient.

In a preferred embodiment of the invention, the driving device includesmeans for moving the male die and/or the ingot container and/or thefemale die and means for applying a pressing force between the femaledie and the male die.

More accurately, the driving device includes means for moving the maledie and/or the ingot container and/or a tool slide including the femaledie, and means for applying a pressing force between the tool slide andthe male die.

As a rule, the female die is a part of the tool slide and is movedtogether with said tool slide. This generally applies to the presentinvention.

The driving device preferably also includes means for moving theextrusion butt shear.

It is understood that the at least one hydraulic advance and/or returncylinder for moving the male die relative to the female die, butparticularly the at least one electric drive for moving the male dierelative to the female die can have the most varied designs.

It is particularly advantageous with respect to the electric drive thatit includes a standard asynchronous motor, since the electric drive canbe designed particularly simply in this way.

In an alternative and likewise preferred embodiment of the invention,the at least one electric drive is an electric servo drive for movingthe male die relative to the female die.

This implements a system concept in which advanced hybrid technology isused to apply the pressing force substantially hydraulically but allother movements of the components of the bar and tube extruding pressare operated electrically, such as the adjustment of the male die into aforce initiating position, the movement of the ingot loader, ifrequired, the movement of the extrusion butt shear and the like.

Finally, the electrohydraulic hybrid drive concept improves energyefficiency compared to the conventional hydraulic drive in that itallows savings on the hydraulic side, preferably through a lower pumpcapacity, a smaller reservoir volume for hydraulic fluid, shorterpiping, and smaller valve sizes. Energy savings can preferably achievedin the electric servo drives by suitable means of energy recovery.

Such a hybrid technology in bar and tube extruding presses has beendisclosed, for example, in the international patent specification WO2013/064250 A1.

It is also preferred in this context that the internal gear pump can bedriven using mixed friction from startup until the desired systempressure is reached. This significantly reduces pulsations generated bythe pump compared to axial piston pumps, particularly in the low speedranges, to the inevitable minimum.

In addition to mixed friction, the at least one internal gear pump canbe cumulatively or alternatively be driven using external hydrostaticlubrication.

It is preferred even without the other features of the invention that amineral oil with a high shear strength is used as hydraulic oil to startthe at least one internal gear pump at the bar and tube extruding presswithout damage, particularly in mixed operation.

It is also preferred that the driving device is connected to a controlunit in which a characteristic curve or a plurality of characteristiccurves for the internal gear pump and/or its drive motor(s) is/arestored. This ensures with simple means that the motors and pumps usedcan be run at their optimum operating point in terms of energy use.Storing the characteristic curves in the software of the control unitallows pressure-dependent direct control of the pumps and/or drivemotors to maintain the desired delivery quantity of hydraulic oil.

It is particularly preferred that the pulsation of the internal gearpump, particularly the preferred internal gear pump, is lower than inaxial piston pumps, preferably by a measure of at least 20%,particularly preferably by at least 30% compared to the pulsation ofconventional axial piston pumps.

It should be noted here once again that the drive concept can beimplemented at significantly lower noise in the present bar and tubeextruding press by using an internal gear pump rather than an externalgear pump.

It is particularly useful with respect to the present driving devicethat the internal gear pump only includes three essential movingcomponents.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Of a bar and tube extruding press or a metal extrusion press 1, FIG. 1essentially shows a base frame. This consists of a cylinder bar 2 and acounter bar 4, not displayed here, which is braced to it by way oftraction sipes 3 (cf. for instance, FIG. 8a). Further contributing tothe frictional connection between these components are pressure columns5, which envelop the traction sipes 3 between the cylinder bar 2 and thecounter bar 4. The pressure columns 5 also serve as guide supports of amale die traverse 6 which is movable in the base frame, and of a movableingot container holder 7. The ingot container holder 7, which holds aningot container or recipient 8, is moved by way of electric motors 12 or13, specifically of servo drives, like the male die traverse 6, whichsupports the advance end of a press piston 11 guided with hydrostaticbearings in its cylinder housing 9 in the counter bar 4 (cf. FIGS. 2through 4). Such an electric motor 12 or 13 is provided on eachlongitudinal side of the ingot container holder 7 and the male dietraverse 6. For the transmission or initiation of the movement, pinionsof the electric motors 12 or 13 comb with toothed racks 14. Screwed ontothe rear end of the cylinder housing 9 of the cylinder bar 2 is acompensation tank 15, and screwed onto the rear wall 16 of thecompensation tank 15 is a cylinder unit 17. In order to upset and pressan ingot 18 loaded into the ingot container 8, the press piston 11 hasan extrusion die 19.

As shown in FIGS. 2 through 4, integrated into the cylinder housing 9 ofthe main or press cylinder is embodied a central filler valve 20, whichconsists of a large-scale valve cover 21 and a cylindrical ring 22 foroperating the filler valve. In the exemplary embodiment, the fillervalve 20, which is shown more closely in FIG. 5, is positioned on anouter tube 23 connected to the rearward end of the press piston 11,interposed by a collar-shaped displacement sleeve 24, on which thecylindrical ring 22 is positioned as well. When applying hydraulic oilto the rearward end of the cylinder piston 25 of the cylindrical ring 22in FIG. 5, the displacement sleeve 24, and therefore the filler valvecover 21, is moved out of its closing position, indicated by solidlines, and into the opening position, indicated by dashed lines, inwhich the filler valve cover 21 enters into a contour adjusted [sic]recess 26 of the press piston 11. In the opening position, a large andfree flow cross-section or ring area is available, through which thehydraulic oil can flow from the compensation tank 15 to the pressurechamber of the cylinder housing 9 behind the press piston 11—and viceversa—without much resistance. In order to draw back the filler valvecover 21 into the closing position, the cylindrical ring 22 is switchedover, so that hydraulic oil is brought before the cylinder piston 25 viathe pressure oil lines, upon which the displacement sleeve 24 with thefiller valve cover 21 is withdrawn correspondingly.

In this case, the outer tube 23 carrying the cylindrical ring 22 withthe filler valve cover 21 is part of a rod assembly 27, which reachesinto the compensation tank 15 and which features a slide plate 28 atthat end, which, when the press piston 11 is charged, moves thehydraulic oil via the open filler valve cover 28, of which FIGS. 2 and 3show the opening position, in the direction of the pressure according toarrow 29 into the pressure chamber behind the press piston 11, or whenthe filler valve cover 21is closed for pressurizing as shown in FIG. 4,into a tank provided adjacent to the press, as shown by the downwardarrow. The rod assembly 27 comprises a pressure bar 31 reaching into theouter tube 23, which is in an operative connection with the cylinderunit 17 which is flange-mounted onto the rearward end or onto the rearwall 16 of the compensation tank 15. The free end of the pressure bar 31features a clamping device 32, via which the pressure bar 31 can bepressed from the inside against the outer tube 23 to [form] a rigidmotion unit with it, when necessary, as in the mode of operation of thebar extruding press 1 for ingot upsetting shown in FIG. 3. The clampingdevice 32 is activated by the combined cylinder unit 17 due to thecorresponding charge of its first coolant path 33.

In an embodiment of the clamping device 32 shown in FIGS. 6 and 7, itfeatures a central spline 34 screwed onto the pressure bar 31, and itsassociated complementary keys 35a, 35b. When the clamping device 32 isnot activated (cf. FIG. 6), the central spline 34 in the drawing left ismoved out forward. When the clamping device 32 is then activated via thecylinder unit 17 (cf. FIG. 7), the spline 34 is pulled by the cylinderunit 17 to the right in the drawing, such that the complementary keys35a, 35b press against the inner walls of the outer tube 23.

The combined electromotive and hydraulic operation of the bar and tubeextruding press 1 will be described in further detail below withreference to FIGS. 8a, 8b through 14a, 14b. FIGS. 8a, and 8b show theingot loading position, in which the ingot 18 to be pressed is broughtinto the center of the bar and tube extruding press 1 with a typicalingot loading device. As can be more clearly seen there, the bar andtube extruding press 1, apart from the previously described components,also comprises tow rods 36 on each side of ingot container holder 7,preferably on each side at the top and at the bottom, of which the freeends are guided through the cylinder bar 2 with freedom of movement (cf.also FIG. 1). The tow rods 36 are assigned to combined cylindrical ringand clamping units 37 that are attached the cylinder bar 2. In the ingotloading position, all moving parts are in the starting position, awayfrom the counter bar 4.

The ingot container holder 7 and the male die traverse 6 with the presspiston 11 and the extrusion die 19 are moved forward in the pressuredirection 29 with an opened filler valve 20 (cf. FIG. 2) by means of theelectric motors 12, 13 to the clamps shown in FIGS. 9a and 9b of theloaded ingot 18 between the extrusion die 19 and the tool or tool set 38of the counter bar 4, with a first quantity of hydraulic oil being movedout of the compensation tank 15 into the pressure chamber behind thepress piston 11. The ingot 18, which is now clamped, is moved into theingot container 8 by moving forward the ingot container holder 7 bymeans of the electric motors 13, as shown in FIGS. 10a, 10b, with thetow rods 36 pulled along when the cylindrical rings and clamping units37 are not activated. In order to seal the ingot container 8 against thetool set 37 [sic], the cylindrical rings and clamping units 37 are nowactivated, and the ingot container holder 7 or the ingot container 8 aremoved by it against the tool 37.

FIGS. 11a, 11b show the resulting pressing or pre-compressing of theingot 18. With the electric motors 12, 13 switched off, the combinedcylinder unit 17 is loaded and the clamping device 32 is activated, sothat the pressure bar 31 is pressed against the outer tube 23.Subsequently, the cylinder unit 17 transfers the pressure force onto thepress piston 11 via the rigid rod assembly 27, consisting of thepressure bar 31 and the outer tube 23. A second partial quantity ofhydraulic oil is moved out into the pressure chamber behind the presspiston 11, as the filler valve is open in this pressure position as well(cf. FIG. 3). The subsequent pressing of the ingot to a remainingextrusion butt 39 is shown in FIGS. 12a and 12b. The clamping device 32is deactivated for pressing, and the filler valve cover 21 of theintegrated filler valve 20 is withdrawn into its closing position shownin FIG. 4 by means of the cylindrical ring 22, sealing the cylinderhousing 9. The pressure force is applied through the feeding ofhydraulic oil from the tank 30 into the pressure chamber behind thepress piston 11, as indicated by the upward arrow show in FIG. 4. Sincethe filler valve 20 is closed and the clamping device 32 is deactivated,a third quantity of hydraulic oil is moved out of the compensation tank15 with the press piston 11, which is moving from the filler valve cover28 of the outer tube 23 in the pressure direction 29. This this quantityof hydraulic oil flows into the tank 30 (cf. FIG. 4).

In order to expose the extrusion butt 39 so that it can be sheared offbefore the ingot container 8, the combined cylindrical rings andclamping units 37 are switched over. The ingot container holder 7 iswithdrawn via the clamped tow rods 36 by the length of the extrusionbutt 39. This operating position after the stripping of the remainingextrusion butt 39 is shown in FIGS. 13a and 13b.

For the preparation of a new loading and pressing process, the ingotcontainer holder 7 and the male die traverse 6 are moved back by theelectric motors 12 and 13 as shown in FIGS. 14a, 14b, with the fillervalve 20 being open to allow the hydraulic oil to flow out of thepressure chamber behind the press piston into the compensation tank 15,and with the clamping device 32 deactivated, and the cylindrical ringsand clamping units 37 deactivated as well, whereupon the bar and tubeextruding press 1 is ready for a new operating cycle.

1. A bar and tube extruding press for forming metal ingots intoprofiles, tubes, billets, or the like, comprising a male die and afemale die, through which a metal ingot can be pressed by means of themale die, comprising a ingot container, and comprising a driving device,in which the driving device comprises at least one main cylinder forapplying the main pressing force of the male die to the metal ingots,characterized in that the driving device on the one hand includes atleast one speed-controlled internal gear pump for supplying hydraulicoil to the at least one main cylinder with which the at least onecylinder can be driven, and on the other hand the driving deviceadditionally comprises at least one hydraulic advance and/or returncylinder for moving the male die in relation to the female die or atleast one electrical drive for moving the male die in relation to thefemale die, by means of which the male die can be moved into a positionin which the speed-controlled internal gear pump only then interactswith the at least one main cylinder in such a way that the main pressingforce is applied to the male die by means of the at least one maincylinder.
 2. The bar and tube extruding press according to claim 1,characterized in that the driving device includes means for moving themale die and/or the ingot container and/or the female die and means forapplying a pressing force between the female die and the male die. 3.The bar and tube extruding press according to claim 1, characterized inthat the at least one electric drive preferably is an electric servodrive for moving the male die in relation to the female die.
 4. The barand tube extruding press according to claim 1, characterized in that theinternal gear pump can be driven using mixed friction from startup untilthe desired system pressure is reached.
 5. The bar and tube extrudingpress according to claim 1, characterized in that the driving device isconnected to a control unit in which a characteristic curve or aplurality of characteristic curves for the internal gear pump and/or itsdrive motor(s) is/are stored.
 6. The bar and tube extruding pressaccording to claim 1, characterized in that the pulsation of theinternal gear pump, particularly the preferred internal gear pump, islower than in axial piston pumps, preferably by at least 20%, preferablyby at least 30%, compared to the pulsation of conventional axial pistonpumps.
 7. A method of forming metal ingots into profiles, tubes,billets, and the like on a bar and tube extruding press having an ingotcontainer, a male die and female die through which a metal ingot ispressed by the male die, a driving device including at least one maincylinder, at least one speed-controlled internal gear pump for supplyingoil to the at least one main cylinder, at least one speed-controlledinternal gear pump for supplying oil to the at least one main cylinder,and one of the at least one hydraulic advance/return cylinder and atleast one electrical drive for moving the male die relative the femaledie, the method comprising the steps of: actuating the one of the atleast one hydraulic advance/return cylinder and the at least oneelectrical drive for moving the male die is a predetermined positionrelative to the female die; and thereafter, actuating the at least onespeed-controlled internal gear pump for supplying oil to the at leastone main cylinder that applies a main pressing force to the mail die forpressing the ingot through the male and female dies.
 8. The method ofclaim 7, wherein the at least one electrical drive is used for movingthe mail die, and the method further comprising the step of forming theelectrical drive as an electric servo drive.
 9. The method of claim 7,comprising the step of driving the speed-controlled internal gear pumpusing mixed friction from startup until a desired system pressure isreached.
 10. The method of claim 7, comprising the step of selectingpulsation of the speed-controlled internal gear pump so that it is lowerthan pulsation of a conventional axial piston pump by at least 20%. 11.The method of claim 10, wherein the pulsation selecting step includesselection of the pulsation of the speed-controlled internal gear pumpwhich is lower than the pulsation of the conventional gear pump by atleast 30%